Sewing machine thread clamping mechanism



p 1953 R. K. HOHMANN SEWING MACHINE THREAD CLAMPING MECHANISM 2 Sheets-Sheet 1 Filed June 8, 1949 WQ/W A T TORNfX Sept. 15, 1953 R. K. HOHMANN SEWING MACHINE THREAD CLAMPING MECHANISM 2 Sheets-Sheet 2 Filed June 8, 1949 INVENTOR. R/CHARQ K f/OHMAA/N ATTORNEY Patented Sept. 15, 1953 UNITED STATES PATENT OFFICE SEWING MACHINE THREAD CLAMPING MECHANISM 2 Claims.

The general object of the present invention is to provide a simple and effective thread controlling mechanism adapted for use in a chain stitch sewing machine to serve as a thread clamp holding the thread against longitudinal movement during the major portion of each stitch forming operation. A more specific object of the invention is to provide a thread controller adapted not only to hold the thread against longitudinal movement during the major portion of each stitch forming operation, but also adapted to serve as a thread tension device, providing all or a major portion of the necessary resistance to over travel of the thread during the remaining portion of each stitch forming operation in which the thread required for the next stitch forming operation is drawn through the thread controlling mechanism.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understandin of the invention, however, its advantages, and specific objects attained with its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described preferred embodiments of the invention.

Of the drawings:

Fig. 1 is a sectional elevation of a sewing machine taken on the line l--l of Fig. 2.

Fig. la is a detailed view of the thread clamping device.

Fig. 2 is an elevation of the upper portion of the sewing machine taken on the line 2-2 of Fig. 1; and

Fig. 3 is a plan view of a portion of the sewing machine.

In the drawings I have illustrated the use of the novel thread controller R; disclosed and claimed herein, in a chain stitch sewing machine of the desirably simple and compact construction illustrated in my prior application, Serial No. 19,275, filed April 6, 1948. As those skilled in the art will understand, however, the improved thread controller is well adapted for use in sewing machines of other types.

The frame of the sewing machine shown in the drawings comprises a hollow base A, a hollow standard B extending upward from the base, and a hollow arm C. The base, standard and arm portions of the frame are integrally connected portions of a light weight hard aluminum casting. The arm portion C is formed with an opening C comprising a main portion extending along the entire upper side of the arm and depending portions at the front side of the needle head portion of the arm and at the opposite end of the arm. The opening C is normally closed by a detachable cover plate C having a horizontal body portion and depending end portions C and C which are detachably secured to the frame in any suitable manner. An electric motor D is mounted in the hollow base portion A of the sewing machine frame. A work bed extension A which may be a steel plate, is screw connected to the base A.

The horizontal motor shaft D carries a small ulley E located beneath the hollow standard B. The pulley E drives an intermediate pulley F through a belt G. The pulley F is secured to a horizontal intermediate or oountershait H, which is journalled in integral portions B and B of the frame standard B. The pulley F is at the inner side of the sewing machine hand wheel F which may be formed integrally with said pulley, or may be detachably clamped against the end of the hub of the pulley F by a clamping nut H on the outer end of the shaft H. Through a sprocket chain or belt I, the shaft H drives the underbed hook shaft J of the sewing machine. The belt I runs over a small sprocket wheel K carried by the shaft H and a larger sprocket wheel L carried by the shaft J at its rear end. The wheel L is in front of and above the motor shaft. At its front end, the shaft J carries a hook J of conventional chain stitch machine type.

In ordinar practice, the motor D may well be a horsepower motor of a universal, commercially available type adapted to operate at about 5900 revolutions per minute under normal load, and to operate at about double that speed when running without load. Such a motor is well adapted for use in driving the sewing machine at the speed required to make about 750 to 800 stitches per minute, when the pulleys and wheels E, F, L and K are proportioned substantially as indicated in Fig. 1, so that the rotative speed of the motor shaft E then required is a little less than seven times the rotative speed of the hook shaft I.

The sprocket wheel L serves as a crank disc carrying a crank pin L. The latter is connected by a link M to a pivot or crank pin N carried by a crank arm N secured to one end of an oscillating needle bar shaft N horizontally disposed in the sewing machine frame arm C. In the desirable construction form shown, the shaft N is pivotally supported by trunnion pivots N which are secured in passages or openings formed in web portions 0C and C of the arm C adjacent the opposite ends of the latter.

The needle bar end of the shaft N carries a crank arm N connected through a link N to a pivot carried by a collar or pivot supporting member 0' which is adjustably secured to the vertical needle bar 0. The latter is mounted in aligned openings formed in a thickened bottom wall portion C of the needle bar end of the arm C, and in the upper web portion 00 of the arm C. The needle bar 0 is provided at its lower end with means for the attachment to the bar of a needle 0 The up and down movement given the needle bar 0 is preferably suflicient to permit the use of a needle 0 of the commercially available, lock stitch type, sewing machine needle.

The sewing machine includes a presser bar P carrying a presser foot P at its lower end which may be of conventional type and is mounted for vertical adjustments in aligned passages formed in the frame parts 00 and C The feed bar X carrying a feed dog X, forms a means for advancing the work over the work bed in the sewing operation. The mechanism employed to give the feed dog its conventional movements may be of any available conventional type, but advantageously, it is of the type disclosed and claimed in my prior application Serial No. 19,276, filed April 6, 1948, and in either event does not need to be further illustrated or described herein.

The thread clampin and tensioning mechanism R, constructed in accordance with the invention claimed herein, is mounted on the cover plate C above a vertically movable pressure actuating or lifting element S. The latter is carried by the crank pin N and operates to periodically reduce or eliminate the clamping pressure on the thread T passing to the needle D as the latter closely approaches the upper limit of its movement away from the work. The thread clamping mechanism comprises an apertured, externally threaded, disc I horizontally disposed on the upper side of the frame cover plate C and rigidly secured thereto. As shown, a plate 2 is interposed between the disc I and plate 0 The end of the plate 2 nearest to the needle bar 0 comprises an uprising portion, bifurcated to provide a thread guide channel 2a. The disc I is secured to the cover plate C by vertical clamping screws 4. Each screw 4 extends through and is in threaded engagement with the wall of a corresponding, internally threaded, vertical passage through the disc member I. The heads of the screws 4 engage a bearing plate 3 shown as received in a recess in the underside of the plate C The screws 4 have unthreaded upper end extensions 4' which serve as vertical guide pins for parts of the clamping mechanism above the disc I.

The externally threaded disc I is in threaded engagement with an annular member 5 surrounding the disc I and for-med with a handle I5 by which the member 5 may be angularly adjusted about the axis of the disc I. The upper and lower end or side surfaces of the member 5 are normally at levels respectively above the upper and lower ends or sides of the disc I, and are raised or lowered by the rotation of the member 5 about the disc I.

The member 5 supports a lower thread clamping disc I having its upper surface slightly above the upper end surface of the member 5. As

shown, the inner upper corner of the annular member 5 is recessed or rabbeted to provide an annular seat for the rim portion of the thread clamping element I. Above the latter is a second thread clamping element in the form of a disc 8. The latter as shown, is received in the space surrounded by the cylindrical flange 9' de pending from the rim of a disc 9, through which the thread damping and tensioning pressure is applied to the disc 8. As shown, a washer-like part 8, which may be formed of leather, in intergoseg between the clamping member 8 and the isc A downwardly acting clamping force is impressed on the member 9 through a bolt or stem I I which has its upper'end screwed into a depending central sleeve or hub portion ID of the member 9. The enlarged lower end or head II of the bolt II serves as a spring abutment engaged by the lower end of a helical bias spring I 2. The latter acts between the head II and the cover plate portion of the hollow arm C, and provides the clampin pressure required to lock the thread between the clamping elements 8 and 9, or the smaller tension pressure on the thread, accordingly as the bolt head II is not, or is operativelyengaged by the actuating member S and held above its normal position. The upper portions 4 of the screws 4, extend through apertures formed in the discs 1, 8, 8 and 9, which are thus held against rotative movement relative to the clamping bolt II, without interference with their vertical adjustments. The thread controller parts mounted on the cover plate portion of the hollow arm C, may be mounted on an integral portion of the arm of a sewing machine frame not including a removable arm part C In operation, as the crank pin N approaches the upper limit of its up and down movement, the previously mentioned member S engages the head II of the bolt II and gives the latter a slight up movement. That movement is sufficient in the normal operation contemplated, to reduce the thread clamping pressure so that the needle may draw enough thread away from the controller R. for the next stitch forming operation. Preferably, however, the thread is left subject to a retarding tension adequate to prevent over travel of the thread away from the controller R. The tension pressure may be increased or diminished, as conditions make desirable, by angular adjustment of the member 5 relative to the disc I with which it is in threaded engagement.

'N but is permitted a slight range of angular adjustment about the latter. To this end, in the particular construction shown, the pin N is formed at one side with a notch N The latter receives the end of a set screw S extending through the portion of the member S at one side of the crank pin H The inner end of the screw S is at such distance from the crank pin axis that it permits the angular adjustment of the block S on the cranl: N through a few degrees, which may be required to permit the fiat underside of the central portion of the bolt head I I to be engaged by the flat upper side of the lifter block S, in each bolt lift operation, without requiring special care in shaping the block or in mounting it on the crank pin N The means provided for supplying the thread T to the sewing machine and for guiding it in its movement from the supply source to the controller R, and from the latter to the eye of the needle, may be of conventional form and arrangement. As shown, the source of thread supply is a spool U mounted in a support W attached to the plate C From the spool U the thread passes to one thread passage in a thread guide Y mounted on a cover plate C between the controller R and the head end of the arm C. From said thread passage the thread passes into the space between the discs '5 and 8 and around the portion of the hollow stem or sleeve Ill and thence back to the thread guide Y and through a second thread passage in the latter. From the last mentioned passage the thread passes around thread guiding parts of a thread guide YA of the pig-tail type mounted on the cover plate C adjacent the head end of the latter. From the thread guide YA the thread passes through a horizontal passage in the upper end of the needle bar and thence through an upper guide YB mounted on the front or face plate end portion C of the cover plate C. From the thread guide YB the thread passes between the tension discs of a tension device Z mounted on the lower end of the face plate 0 From the tension device Z the thread passes through a thread guide YC of the pig-tail type mounted on the face p1ate C adjacent the tension device Z. From the guide YC the thread passes to the eye of the sewing machine needle 8*. In ordinary practice it is contemplated that the tension device Z will subiect the thread to an appreciably smaller tension than does the mechanism when the latter is ad usted to permit the thread to be drawn through the space between the clamp ng discs I and 8.

It is believed that the construction and operation of my im roved thread controller will be readily a parent from the accompanying drawings and the fore oing description.

While in accordance with the provisions of the statutes, I have illustrated and described the best form of embodiment of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention as set forth in the appended claims, and that in some cases certain features of my invention may be used to advantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In a chain stitch sewing machine comprising a frame including a work support and an elevated hollow arm, a rotary hook mounted in said frame below said support, a reciprocating needle bar mounted in said arm and carrying a needle at its lower end, mechanism for rotating said hook and reciprocating said needle bar in timed relation to form chain stitches and including a needle bar shaft mounted in said hollow arm to turn about an axis transverse to a plane including the needle bar axis; the combination controlling the passage of thread to said needle including a normally stationary thread clamping element external to and supported by said arm, a movable thread clamping element external and supported by said arm and movable toward and away from the latter into and out of a position in which said thread is gripped between said elements and thereby held against longitudinal movement, a threaded connection between said normally stationary element and said arm for adjustment of that element toward and aw y f Q said arm, said movable element comprising a stem extending into said hollow arm, a bias spring within said arm and acting between the latter and said stem to bias said movable element for movement toward said arm and an actuating part within said hollow arm and pivotally connected thereto to oscillate about a horizontal axis laterally displaced from said stem, and arranged for connection to said mechanism for oscillation of said actuating part in time relation to the reciprocating movement of the needle bar, and including a portion arranged for oscillating movement toward, into and out of engagement with, and away from the end of said stem and thereby give said movable element a small movement away from said normally stationar element to permit longitudinal movement of the thread as the needle bar approaches the upper limit of its range of reciprocating movement.

2. In a chain stitch sewing machine comprising a frame including a work support and an elevated hollow arm, a rotary hook mounted in said frame below said support, a reciprocating needle bar mounted in said arm and carrying a needle at its lower end, mechanism for rotating said hook and reciprocating said needle bar in timed relation to form chain stitches and including a needle bar shaft mounted in said hollow arm to turn about an axis transverse to a plane including the needle bar axis; the combination controlling the passage of thread to said needle includin a normally stationary thread clamping element external to and supported by said arm, a movable thread clamping element external to and supported by said arm and movable toward and away from the latter into and out of a position in which said thread is gripped between said elements and thereby held against longitudinal movement, said movable element comprising a stem extending into said hollow arm, a bias spring within said arm and acting between the latter and said stem to bias said movable element for movement toward said arm and an actuating part within said hollow arm and pivotally connected thereto to oscillate about a horizontal axis laterally displaced from said stem, and arranged for connection to said mechanism for oscillation of said actuating part in timed relation to the reciprocating movement of the needle bar, and including a portion arranged for oscillating movement toward, into and out of engagement with, and away from the end of said stem and thereby give said movable element a small movement away from said normally stationary element to permit longitudinal movement of the thread as the needle bar approaches the upper limit of its range of reciprocating movement, and a tubular element surrounding said stem and anchored to said arm, said normally stationary threaded clamping element being in threaded engagement with said tubular element so that the normally stationary element may be moved toward and away from the arm by rotative adjustment relative to said tubular element.

RICHARD K. I-IOHMANN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 298,315 Ryder May 6, 1884 347,777 Diehl Aug. 24, 1886 423,996 Harlow et a]. ,.-i Mar. 25, 1890 1,525,643 Fifield Feb. 10, 1925 

